1. Field of the Invention
The present invention relates to the plasma processing of substrates. More particularly, the present invention relates to an apparatus for generating and deflecting a plasma jet for treating substrates using a plasma jet treatment process.
2. Description of the Prior Art
Published application No. PCT/SU90/00286 describes a method for plasma processing of a material consisting of a system of more than two meeting plasma jets which form a mixing zone wherein a material to be processed is fed into the mixing zone. Direct electric currents are passed through sections of the plasma jets up to the mixing zone and a magnetic field is applied to the current conducting sections of each plasma jet. The apparatus for plasma processing of material described in the application comprises a charge conduit, an electric arc plasma jet generator further comprising a plurality of electrode units for generating the plasma jets. The electrode units are oriented at acute angles to an axis of the charge conduit and are connected to a direct current source. The apparatus further comprises a magnetic system formed from an open magnetic circuit with poles located in a mixing zone of the plasma jets. The apparatus described in PCT/SU90/00286 has very limited abilities to control direction of each plasma jet independently so as to control the structure of combined plasma flow.
Published application No. PCT/SU90/00287 describes an apparatus for plasma-arc processing of material. The apparatus comprises a charge conduit which is surrounded by a plurality of electric arc plasma jet generators and a magnetic system. The generators comprise two electrode assemblies. Solenoids are mounted on poles of the magnetic circuit. The apparatus can be used only if the plasma jets are directed towards the axis of the apparatus with angles more than 45 degrees. If the angles are less than 45 degrees then the magnetic system itself causes instability in each of the plasma jets and the combined plasma flow. Another disadvantage is that each plasma jet orientation can be controlled only when it is located in equilibrium position within a narrow zone near the corresponding basic plane where both a second and third magnetic field interacts with it. If the plasma jet is deflected relatively far from the basic plane then the effectiveness of the control significantly reduces because only one of these magnetic fields interact with the plasma jet.
In published Russian Patent No. 2032281, a method and apparatus for plasma flow production is described. Plasma jets are formed by any method and are directed symmetrically to the axis of a common plasma flow at an angle less than 45 degrees. Direct current is passed along each plasma jet in opposite directions relative to the common axis and external magnetic fields are applied to each jet. The 1st magnetic field is applied between the axis (4) of each jet and the common axis, while the 2nd and 3rd fields are applied to the half-spaces between the axes. Interaction of the magnetic fields and the current in the jet causes deflection of the jets from their axes (2). The induction of the fields are adjusted, to ensure the axis (4) of the jets are parallel to the common axis after interaction and the configuration of the external magnetic fields is selected to increase the stability of the plasma jets. During random slight displacements of the jets, inductance to one side increases and decreases to the other side, to ensure return of the axis of the jet to a direction parallel to the common axis. The disadvantage of the above described method and apparatus is that the method can be realized and correspondingly the device can be used only if the plasma jets are directed to the device axis with angles less than 45 degrees. If the angles are more than 45 degrees then the magnetic system itself induces instability of every plasma jet and the combined plasma flow. Another disadvantage is that each plasma jet orientation can be controlled only when it is located in an equilibrium position within narrow zone near the corresponding basic plane where both second and third magnetic fields interact with it. If the plasma jet is deflected relatively far from the basic plane, then the effectiveness of the control significantly reduces because of only one of these magnetic fields interacts with the plasma jet.
Russian patent document RU 2059344 discloses a plasma generating device including electrode units having a magnetic system comprising a pair of U-shaped members or poles and a solenoid. The ends of the poles are located in the space defined by the symmetrical planes intersecting the axis of symmetry of the device. However, the poles are not arranged in a manner to provide perpendicular magnetic fields for steering the plasma.